Add a content API to create a message channel.

content/public/browser/message_port_provider.h

+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_PROVIDER_H_
+#define CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_PROVIDER_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class WebContents;
+
+// An interface consisting of methods that can be called to use Message ports.
+class CONTENT_EXPORT MessagePortProvider {
+ public:
+  // Posts a MessageEvent to the main frame using the given source and target
+  // origins and data. The caller may also provide any message port ids as
+  // part of the message.
+  // See https://html.spec.whatwg.org/multipage/comms.html#messageevent for
+  // further information on message events.
+  // Should be called on IO thread.
+  static void PostMessageToFrame(WebContents* web_contents,
+                                 const base::string16& source_origin,
+                                 const base::string16& target_origin,
+                                 const base::string16& data,
+                                 const std::vector<int>& ports);
+  // Creates a message channel and provide the ids of the message ports that are

[jochen (gone - plz use gerrit), 2014/11/19 08:49:20]

nit empty line above this line

[sgurun-gerrit only, 2014/11/19 19:16:21]

Done.

+  // associated with this message channel.
+  // See https://html.spec.whatwg.org/multipage/comms.html#messagechannel
+  // Should be called on IO thread.
+  static void CreateMessageChannel(WebContents* web_contents,
+                                   int* port1,
+                                   int* port2);
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(MessagePortProvider);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_PROVIDER_H_